Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.50	11.220%	$233.0059	$233.01	$233.00	$233.00
Purchase #2	$67.99	6.303%	$72.2754	$72.28	$72.30	$72.30
Purchase #3	$111.47	3.678%	$115.5699	$115.57	$115.55	$115.60
Purchase #4	$145.87	3.240%	$150.5962	$150.60	$150.60	$150.60
Purchase #5	$122.86	5.602%	$129.7426	$129.74	$129.75	$129.70
Purchase #6	$113.96	6.694%	$121.5885	$121.59	$121.60	$121.60
Purchase #7	$52.51	3.836%	$54.5243	$54.52	$54.50	$54.50
7 purchase totals =	$824.16		$877.3028	$877.31	$877.30	$877.30